The present inventor has described, in his U.S. Pat. Nos. 5,249,322; 5,056,441; and 4,985,953, assigned to Louisville Bedding Co., fitted mattress coverings which make highly advantageous use of a skirt constructed of material which is stretchable in its longitudinal dimension, i.e., horizontally about the periphery of a mattress upon which it is installed. Such a construction provides a firm grip on the mattress to thereby prevent shifting of the cover on the mattress during use, and to accommodate mattresses of differing thicknesses and peripheral dimensions (length and width), while pulling the skirt in tightly against and underneath the mattress so as to avoid sag or loose fabric otherwise creating a sloppy appearance.
In one embodiment of the aforementioned Seago patents, the depending skirt is formed from a separate strip of material which is attached about the periphery of an inelastic top panel of the mattress covering, e.g., mattress pad. The separate strip comprises a gathered single layer of substantially inelastic fabric material with a plurality of spaced-apart parallel, elongated cords, such as elastic strips or yarn, stitched into the inelastic skirt material so as to extend generally perpendicularly to the longitudinal axes of folds of gathers which form with the elastic cords being in a relaxed condition prior to the installation of the cover on the mattress.
In another embodiment of the above-mentioned Seago patents, the skirt comprises side and end panels formed as unitary extensions of the top panel. These panels are stitched together at their ends to form closed corners of the mattress cover, and the skirt thus formed is made stretchable by stitching into the panels elastic cords under tension, which, when permitted to relax, form gathers similar to the first embodiment.
Mattress pads constructed in accordance with the teachings of the above-mentioned Seago patents have met with substantial commercial success. The present assignee's Expand-A-Grip® mattress pads, which are covered by the patents, are industry leaders. The principles described in the Seago patents are fully applicable to fitted sheets as well. However, the marketplace adoption of the constructions in sheets has been significantly lower.
This is believed to be due, at least in part, to the sensitivity of users and purchasers of bedding products with respect to the appearance and feel of a fitted sheet when it is installed and used on a mattress. The sides of a fitted sheet installed on a mattress receive much more exposure, both visually and to touch, than do the sides of a fitted mattress pad. Whereas the sidewall of a mattress pad generally remains covered by an overlying fitted sheet during use, a fitted sheet is revealed upon the drawing back of a top sheet and blankets or other bed coverings. As a result, consumers of bedding products may favor a sheet that provides an uninterrupted continuation of the sheet material (e.g., a high thread count woven cotton fabric) from the main (top) panel to the sidewalls. A fitted sheet having its skirt constructed of a separate elasticized strip of material attached to and extending about the entire periphery of a separate top panel would, of course, not provide such an uninterrupted continuation of the sheet material.
The look/feel issue mentioned above may be alleviated somewhat with the second one of the above-mentioned embodiments of the Seago patents, since in that embodiment, the side panels are provided as integral extensions of the top panel. Thus, the construction provides a continuous wrap-around of the upper edge of the mattress, which extends down to the first line of stitched-in elastic cord. As illustrated in the Seago patents, typically this first line of cord would be spaced downwardly from the top surface of the mattress. This construction also has the advantage of forming well defined closed corners for neatly fitting the corners of the mattress. Nonetheless, the appearance of the lines of stitched-in elastic cord may be viewed as an undesirable deviation from the conventional uninterrupted extension of the main panel material over the full depth of the mattress.
As a variation on the above-described mattress cover constructions of the Seago patents, Whitely U.S. Pat. No. 5,530,979, assigned to Perfect Fit Industries, proposes to provide a two-part skirt construction. A first upper part of the skirt (an inelastic side skirt) is provided as an integral extension of the inelastic material used to form the main panel serving to cover the mattress top side. A second (lower) part of the skirt (elastic underskirt) is formed by a strip of material attached to the bottom edge of the side skirt about its entire periphery, and is made elastically stretchable in its longitudinal dimension, i.e., peripherally about a mattress on which it is installed, for contraction under a mattress. A variety of known elastically stretchable fabric constructions are used to form the second elastic part.
In a manner similar to the above-mentioned second embodiment of the Seago patents, such a construction reduces the coverage area of the elastic material, and also permits the formation of well-defined closed corners. Nonetheless, a seam attaching the strip of elastic material to the inelastic side skirt, as well as the differentiated elastic material itself, will be present and visible along the mattress sidewalls when the construction is used in a fitted sheet. Thus, the aesthetics and touch/feel related drawbacks mentioned above persist.
Isham U.S. Pat. No. 4,672,702 discloses a mattress covering comprising a main panel provided with mattress sidewall covering extensions. These extensions are provided with rectangular cut-outs at their corners. The cut-outs accommodate the ends of stretch fit end panels having a length exceeding the width of the mattress upon which the cover is to be installed, such that when the cover is installed the stretch fit panels wrap around the corners of the mattress. Each stretch panel is sewn along its upper edge to a corresponding end edge of the main panel, which in turn lies in registry with an end edge of the mattress top surface periphery. The ends of the stretch end panels are sewn to corresponding edges of the cut-outs provided in the mattress sidewall covering extensions. Isham discloses that stretch fabrics suitable for use in forming the stretch panels are typically elastic in only one direction, and that when such materials are used the rectangular stretch panel should be cut such that the stretch takes place along a line perpendicular to the panel's long edge, i.e., to provide stretchability in the up and down direction.
The Isham configuration has the drawback of not providing significant stretchability in the peripheral direction of the skirt. Such peripheral stretchability in a skirt has proven to be much more effective than up-down stretch in providing a secure grip on a range of mattress sizes and thicknesses. Moreover, in the case of a fitted sheet construction, the extension of the stretch end panels about the four corners of the mattress, into sidewall regions at the head and foot ends of the bed, detrimentally places differentiated elastic material along sidewall areas which are exposed upon the drawing back of a top sheet, blanket and/or other bed covering.
Johnson, III U.S. Pat. No. 4,980,941 discloses a fitted bedding product wherein portions of side panels thereof are formed of elastic material. In particular, Johnson, III teaches use of stretch panels formed from a three layer laminate construction (with seams extending vertically). One disclosed embodiment includes a configuration of corner encompassing stretch end panels which appears to be generally similar to that disclosed by the Isham patent, including the attendant shortcomings.
Kardell et al. U.S. Pat. No. 5,287,574, shown on its face to be assigned to Restful Knights, proposes a fitted mattress covering which employs elasticized head and foot panels. An upper edge of each panel is secured, by conventional sewing methods, to a top portion of a unitary main panel of the mattress cover. The ends of the head and foot panels are sewn to corresponding ends of overhanging first and second side portions of the unitary main panel. The elasticized head and foot panels are provided in a trapezoidal shape, such that the bottom edges of the head and foot panels have a shorter length than those panels' top edges. According to the patent, this will cause the head and foot panels to exert greater tension on the side portions of the main panel near the lower edges thereof, to assure a secure fit for a range of mattress thicknesses.
The Kardell et al. trapezoidal panel configuration, and the manner of its attachment to the main panel, are such as to induce an elastic recovery force that increases linearly from essentially zero at the point of attachment of the top edge (where the elastic material is unstretched at the time of being bound to the main panel material) to a maximum along the bottom edge (where the greatest amount of stretch is required to attach the end panels to the ends of the overhanging side portions of the main panel). As a result, the ability of the mattress covering to grip tightly to the mattress and avoid shifting may be compromised, especially at an upper portion of the corners of the mattress sidewalls and end walls, where loose material may also create a sloppy appearance. Additionally, the corner seams may become distorted as a result of the non-uniform tension forces, leading to a degraded fit and appearance at the corners.